1. Field of the Invention
The present invention relates to a data conversion processing apparatus that performs resampling processing of digitally sampled voice and images.
2. Description of the Related Art
Digitally sampled voice and images require various kinds of processing for connection to a speaker and CRT or similar display apparatus respectively. For example, in the case of voice, if the sampling frequency is different for input and output, resampling of the input data is necessary using a low pass filter and linear interpolation, and if it is wished to obtain one output from a plurality of inputs, superimposition of the respective data is also necessary after resampling.
An example of a conventional data conversion processing apparatus is given in Patent Document 1 (Unexamined Japanese Patent Publication No. HEI 8-321745). A conventional data conversion processing apparatus will be described using FIG. 11.
The conventional data conversion processing apparatus shown in FIG. 11 has memory 1, a resampling section 2, a superimposition section 3, and a control section 4.
Resampling section 2 selects one of a plurality of inputs, performs high-frequency component cutting by means of a low pass filter and arithmetic computation using linear interpolation or spline interpolation, and writes the result to memory 1. Filter processing in resampling section 2 is possible for a number of samples of an M/N integral ratio with good frequency characteristics using zero point insertion and thinning-out, but fine adjustment of the number of samples is not possible. Therefore, a filter processing result is converted to an arbitrary number of samples using linear interpolation or spline interpolation. Also, a low pass filter is selected as the filter, and in order to perform distortion-free processing in voice processing and so forth, this is normally limited to a finite impulse response (FIR) and bilaterally symmetrical linear phase type. The above work is executed by time division, and processed data is stored in areas of memory 1 corresponding to the plurality of inputs.
Superimposition section 3 adds and outputs results after a plurality of resamplings stored in memory 1 as being of the same frequency. Superimposition section 3 performs not only addition but also multiplication for gain adjustment of the respective input sequences. These are processed by time division.
Control section 4 performs time division control of resampling section 2 and superimposition section 3 according to the input data. By the above-described means, a plurality of input data are subjected to time division processing and output data is obtained efficiently.
However, a problem with the above-described conventional technology is a lack of flexibility in that control of input and output is fixed, and therefore a plurality of outputs cannot be obtained, and neither can resampling processing be repeated with output data as input data, for example.
For example, two-dimensional—that is, image-processing is possible if one-dimensional processing results are stored and one-dimensional image processing is performed again in the orthogonal component direction, but to do so requires the addition of control enabling use of the data conversion processing apparatus again.